单项选择题

It is delight to fly at the Pole because there _______.

A．planes fly higher than at the equator
B．the eyes can reach about 4,000 meters
C．planes are clear of bad weather
D．planes fly more quickly than at the equator

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单项选择题

Today, compared with 1910 _______.

A．five times fewer patients die after being operated on
B．20 percent fewer of all operation patients die
C．20 percent of all operation patients recover
D．operation deaths have increased by 20 percent.

单项选择题

What are some of the more astonishing innovations in modem surgery

A．Ears, nose and throat transplants.
B．Values plastic hearts.
C．Plastic heart valves.
D．Leg transplants.